Grow Cubes


Reviews & Questions


  • Pot based growing with ’rockwool’
  • High quality Grodan brand.
  • Homogenous and high quality
  • Ideal for drip irrigation systems
  • Ultimate control over pH and EC
  • No mess!
  • Cost effective hydroponic substrate

Growing with Grodan rockwool offers the modern day indoor grower the opportunity grow like a commercial greenhouse grower, from the comfort of your own garden. Using Grodan rockwool as a substrate gives the grower ultimate control over the EC, pH and moisture content - ultimately meaning you can steer your plants towards the perfect harvest.

Grodan have an extensive manufacturing process that ensure you receive the finest quality of rockwool substrate, every time you buy. Grodan are a cornerstone of the commercial hydroponic sector, you will struggle to find a better product on the market!

Typically, you would see rockwool as a block or slab, however these small 1cm cubed bits of rockwool have been developed to give all the benefits of rockwool, but for the use in a more traditional pot based irrigation system. For those wanting to make the leap to growing with rockwool, but don’t want to make drastic changes to existing pot-based irrigation systems, these grow cubes provide the perfect solution.


Grodan rockwool cubes are made from natural minerals, primarily basalt volcanic rock. The material is then turned molten by heating it up to roughly 1600°C. The heated mass is then spun in several directions until a candyfloss like texture has been achieved. The required sized cubes are then cut out from the mass once it has correctly cooled. This process gives Grodan rockwool cubes unique properties for growing hydroponically that mean it has fantastic advantages over traditional gardening substrates.


Using stonewall as a hydroponic substrate gives you the edge over traditional growing media for your indoor garden. Specifically, these advantages relate to its water holding properties and EC/pH control.


Firstly, the water holding capacity is much greater, meaning litre for litre it can hold substantially more water than coco coir or soil. Secondly it releases this water much easier than soil or coco does, so the plant doesn’t use as much energy obtaining the water from the substrate. This means you can use a lot smaller volume of media, and your plant has more energy available for vegetative or generative growth above ground. Maximum efficiency in almost every way!


By keeping a close eye on the run off water after each irrigation, you can monitor and control the EC and pH of rockwool to a much more precise degree than any other substrate can offer. A plant’s requirement for nutrient changes throughout its entire life cycle and rockwool allows you to respond to these changes almost instantly. This means you can maximise your plants’ performance at every key stage and really push the limits of your potential yield. Try to aim for a run-off of roughly 10% for each irrigation, too much run-off will give you a false indication of what the levels are actually inside the block.


Before you plant out into the Grodan rockwool cubes you need to quickly treat them so the pH and EC levels are correct. Ideally, first soak all the cubes in a low pH solution (pH 4.5-5) and then allow them to drain. After this you then simply irrigate through the pot with a solution set to the required EC and pH levels and allow to drain slightly before transplanting into.


Try to ensure your irrigation evenly disperses the water over the entire surface of the pot. This will ensure every bit of rockwool in the pot is as evenly saturated as possible.

Although beneficial bacterial /fungal products can be used (to a degree) with Grodan blocks, it is often best practice to keep the entire system as sterile as possible.

Reviews & Questions

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